The lines that can be found in images are very powerful elements that with a little practice can add dynamic impact to a photograph in terms of mood as well as how they lead an image’s viewer into a photo.
Horizons are the most common horizontal line to be found in photographs and they often act as a dividing point in a photograph – in effect an anchor that the rest of the image is formed around.
Layers of horizontal lines can create rhythm or patterns in an image that can become the focus of an image in and of itself. Unbroken horizons can often lead to a photograph feeling somewhat static or dull and a good strategy is to use other shapes in the landscape you’re photograph to break things up. Horizons should generally not be placed in the middle of your frame. A much more effective technique is to place them in the upper or lower third of your frame.
Vertical lines have the ability to convey a variety of different moods in a photograph ranging from power and strength to growth. As horizontal lines can be accentuated by shooting in horizontal format, vertical lines can be used very effectively by swapping the way you hold your camera into a vertical framing. This lengthens the vertical subject further which can emphasize its height.
It’s important to attempt to keep your vertical lines as much in line with the sides of your image as possible. This is not always possible if you’re shooting looking up an image as the subject will taper off towards the top – but attempt to keep its center as straight as possible and you should be ok.
Learning how to use lines in photography doesn’t just happen. It takes time and practice to become good at it.
(photos and the text are quoted from the digital photograph school)